Problem: Simplify the following expression: $k = \dfrac{z + y}{x + 6y} - \dfrac{2y}{x + 6y}$ You can assume $x,y,z \neq 0$.
Answer: Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{z + y - (2y)}{x + 6y}$ $k = \dfrac{z - y}{x + 6y}$